This invention embodies primary operational features of the tools disclosed in my two previous U.S. Pat. Nos. 3,507,173 (Apr. 21, 1970) and 3,584,694 (June 15, 1971); however, in addition, it incorporates certain structural and operational features not disclosed therein.
More particularly, the additional structural and operational features of the present invention not found in the tools of my two patents supra, can be summarized as follows:
1. The shaft that connects the dual drive planetary gearing with the output gearing does not pass through the center of the rotor of the main motor. Accordingly, the rotor can be of reduced diameter because the blades can extend further into the rotor axis since such space is not occupied by a rotor shaft, as in the case of the structure of the tools disclosed in my prior patents supra.
2. The main motor is coupled to the ring gear i.e., reduction gear cage, of a dual drive planetary gearing through spur gearing, whereby the ring gear rotates at some ratio of main motor speed, thus providing ring gear rotation at less speed than that of the main motor.
It will be apparent that features of smaller diameter rotor size, as well as the lower rotation speed of the dual drive ring gear, both contribute to a reduction in kinetic energy, thus generating lower torque values without errors in torque readings because of stored energy in the rotating parts.